The present invention relates generally to pneumatically operated graduating release valve devices for railroad vehicles and more specifically to an improved graduated release valve which is capable of operating in the graduated release or the direct release mode.
Graduating release brake control devices currently being used on passenger rail vehicles are of the general type known as 26-C. Direct release brake control devices, however, have been used on freight rail vehicles to provide improved responsiveness during brake application mode and freedom from sticking brakes on long trains during the release mode. Such a brake control device is generally known as an ABDW brake control device for freight vehicles, which is of the type generally disclosed in the Wilson U.S. Pat. No. 3,232,678, representing the well known ABD valve device, combined with a continuous quick service portion as disclosed in the Wilson U.S. Pat. No. 3,716,276.
Freight cars in the western hemisphere generally include a single pipe AAR-type direct release valve. This is in contrast to the two pipe, graduated release valve systems for passenger trains in the U.S. which include a two pipe system, namely generally a brake pipe and a rail supply pipe. UIC-type equipment, which is also freight equipment, is equipped with a two pipe, graduated release system. The UIC systems for freight generally do not include greater than 50 cars and therefore the ability to use graduated release is not detrimental.
The desirability of using the advantages of the ABDW freight control valve on passenger trains with a graduated release brake control device is described in U.S. Pat. No. 4,775,194 to Vaughn, et al. The graduated release valve is governed generally by the brake cylinder pressure, brake cylinder exhaust passage pressure from the ABDW control valve and brake pipe pressure, to at times, modify the output of the control valve device to provide for graduated control of the passenger railroad vehicles brakes. The ability to switch between direct release and graduated release is produced by manually changing a specific fluid connection 85 on the graduated release valve. Another example is U.S. Pat. No. 4,033,632 to Wilson wherein valve cover 15 is removed and gasket 15a is rotated to adjust between direct and graduated release. This similar adjustment is provided on the 26F control valve in prior art brake systems.
The mixing and matching of freight cars in various systems throughout the world including freight cars with the AAR single pipe system and freight cars with the UIC double pipe system is occurring more frequently. One cannot always guarantee that the manual adjustment from a direct release to a graduated release has been effected in the yard. Freight trains were generally designed for long trains and therefore have direct release. Thus freight train car brakes cannot be used in short trains with UIC style two pipe, graduated release freight systems.
Another piece of rail equipment which includes a two pipe system is the road railer. This is a vehicle which is equipped to run on rails as well as on the road. The rail supply line is used for the rail brakes and the highway supply line is used for the highway brake system. Thus there exists the desirability of incorporating these types of vehicles within a train capable of operating in a direct release and a graduated release train system.
Thus it is an object of the present invention to provide an improved graduated release valve for rail vehicles.
Another object of the present invention is to provide a graduated release valve for rail vehicles which automatically selects between the direct release mode and the graduated release mode.
These and other objects are achieved by providing a graduated release valve which includes control valve port, brake cylinder port, brake pipe port, graduated volume port and a supply line port. A valve, for example a graduating check valve, is provided connecting the control valve port and the brake cylinder port which prevents flow from the brake cylinder port to the control valve port. A graduating section controls the valve to produce graduated release of the brake cylinder in response to pressure on the brake cylinder port, brake pipe port and graduated volume port. An automatic mode section controls the valve to produce direct release of the brake cylinder in response to less than a predetermined value of pressure on the supply line port. If it is a two pipe system which includes graduated release, an appropriate pressure will appear on the supply line port and therefore allow the valve to be controlled by the graduating section. If less than a predetermined pressure is on the supply line port indicating that it is a single pipe system, the mode selecting section maintains the valve open such that it operates as a direct release valve between the control valve port and the brake cylinder port.
The valve includes a stem which is operated on by the graduating section and the mode section to control the operation of the valve. The mode section includes a pressure member cooperating with the stem and a spring for defining the predetermined pressure and biasing the pressure member to move the stem to open the graduated check valve. A pressure chamber is connected to the supply line port, moving the pressure member in response to the predetermined pressure on the supply line port to prevent cooperating between the pressure member and the stem such that the stem can be operated by the graduating section. Preferably the predetermined pressure is in the range of 50 psi or greater.
The graduating section includes a brake cylinder pressure chamber connected to the brake cylinder port for moving the stem to open the graduating check valve. A brake pipe pressure chamber is provided connected to the brake pipe port for moving the stem to open the graduating check valve. A graduating volume pressure chamber is provided connected to the graduating volume port moving the stem to close the graduating check valve. A first diaphragm is connected to the stem between the brake pipe and the graduating volume pressure chamber and a second diaphragm is connected to the stem between the brake cylinder pressure chamber and an exhaust pressure chamber. The first diaphragm's area is two and one half times the second diaphragm's area. A spring is provided in the brake pipe pressure chamber for moving the stem to open the graduating check valve at 5 psi. This assures direct release of the brake when the pressure in the brake pipe is below 5 psi.
A charging check valve is provided between the brake pipe and the brake cylinder pressure chambers for charging the graduating volume from the brake pipe. An overcharge check valve is provided between the brake pipe and the brake cylinder pressure chambers for discharging the graduating volume into the brake pipe. The overcharge check valve includes a spring biasing the overcharged check loads for pressure differentials of less than 30 psi. This prevents discharging of the graduating volume during the early stages of brake application.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.